The principal objctive of the proposed research is to elucidate the relationship between the process of sexual differentiation of the brain and the hypothalamic regulation of food intake and body weight. To date, sexual morphism in the latter control process appears to be restricted to chronic or long-term regulation. Moreover, the responsiveness to the food intake suppressing action of estrogen is a central component of this dimorphism. The proposed research is divided into two segments which all attempt to elucidate this action of estrogen. In one, the possible neurochemical correlates of estrogen action on food intake will be investigated by monitoring catecholamine turnover and glutamic acid decarboxylase activity in specific brain regions. In the second, the possible mechanism of the food intake suppressing effect of estrogen will be investigated at the behavioral level, e.g., does estrogen render a meal more satiating? Finally, the relationship between long and short term regulation of food intake will be studied by evaluating the effects of estrogen in animals in which short term regulation is disrupted by vagotomy or lesions of the lateral hypothalamus. It is hoped that these studies will elucidate the interaction between gonadal activity and the regulation of food intake and body weight in the adult and developing animal. BIBLIOGRAPHIC REFERENCES: Young, J. K., Nance, D.M. and Gorski, R.A. Sexual dimorphism in the response to different diets. Program Ann. Meeting, Soc. Neuroscience, Toronto, Canada, 1976, p. 295 (abstract). Sieck, G.C., Nance, D.M., Ramaley, J. A., Taylor, A.N. and Gorski, R.A. The presence of a 4-day cycle in feeding behavior prior to puberty in the female rat. Program Ann. Meeting, Soc. Neuroscience, Toronto, Canada, 1976, p. 440 (abstract).